WO-A-01/62689 describes a process for converting oxygenate to an olefin-containing product wherein oxygenate is introduced into a reactor system at plural stages along a flow axis of a reactor catalyst bed. For reactions of methanol over ZSM-34, SAPO-34, and of methanol with toluene over ZSM-5 catalysts, in a fluid-bed reactor it was shown, that ethylene selectivity improved when multiple feed injectors were used.
However, in the known process, improved selectivity is accompanied by a lower methanol conversion. In the experiments with ZSM-34 in Example 1, a significant amount of methanol remained unconverted. Also for SAPO-34, a decreasing conversion with increasing number of injectors is found. In the known process conversion of oxygenate is therefore already a problem at the relatively low reaction temperatures of between 375-470° C. In view of the lower conversion it is proposed to increase the catalyst activity, or to allow a lower conversion, optionally followed by a recycle of unreacted oxygenate. Increasing the reaction temperature is not an option, as this increases the deactivation of the catalyst.
There is a need for an improved process for the conversion of oxygenate to olefin in which the selectivity towards desired olefin species, in particular ethylene, can be increased while providing sufficient activity and stability so that high oxygenate conversion can be realized in an industrial-scale process.